QRP Station > Antennas

a 34ft doublet, ladder line, a balun & remote tuner

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KO7I:
I call my antenna a doublet because it is non-resonant, fed with ladder line and used on multiple bands above 20M.
Today i did some more playing with my antenna and had a ball. 15M was open, where was everyone?
Normally I feed this antenna with 100 ft of RG-213 which connects to a DX Engineering 4:1 balun rated at 10kw peak. from the balun I use 100ft of ladder line to the antenna that is 35 ft high. With this setup I have a lot of transmission line loss.
Today I moved my MFJ 929 auto tuner out to the 4:1 balun and installed a bias tee inside the shack. It worked very nicely. I was able to make multiple QSO's answered several CQ's on SSB on the east coast running 5W. I also made a couple contacts on CW. I played around on 20M too and I was working very well too.
It has really paid off to reduce the coaxial cable losses across the 100 ft run.
Basically I went from struggling to making qso's on the higher HF bands with ease, I was able to work almost everyone I could hear - except for the VK9EX dx-pedition to Christmas Island. HI HI.
Chasing the SOTA activations has been a hoot. Doing QRP to QRP is fun.
I think I will begin looking for a ammo can to put the MFJ 929 auto tuner inside for this winter.

Vy 73, Don KO7i

G0BVZ:
Hi Don, sorry I was so slow in coming back with my two penn'orth.

One day I dispensed with coax and balun and obtained an MFJ-974HB. I ran 300ohm slotted feeder from the shack all the way to the feed point of the longest inverted V doublet I could fit into my plot. It was a BIG improvement for both tx & rx. I can operate on all hf bands and the brutal simplicity of the balanced setup really appeals to me.  Why 300ohm slotted? -Because it catches the wind less than 450ohm twin, which is an important consideration when the antenna support is a 12m Spiderpole. ;D
(I've reached that stage in life where going aloft ain't so smart: those light glass fibre masts are a real game changer for me.)

Three observations:-
1) There is great merit in simplicity
2) Those old time hams knew a thing or two about antennas!!
3) Not using a balanced tuner is a compromise. Just sayin'.

73,

Vic /Ship's Cat

sm5mek:
As i can see it is an double Zepp, dipole with random lenght and feeded with ladder. See more here.  :D

G0BVZ:
The good people at Sotabeams  (a local company for me) have an info page at url

http://www.sotabeams.co.uk/a-simple-multi-band-doublet-for-portable-operating/

The venerable multiband doublet is described there: it also mentions that the doublet is one of Cebik's "Top Five Backyard Multi-band Wire HF Antennas" which is good enough for me!!    ;D

True open wire feed is most efficient, but I prefer the advantages of good slotted 300ohm feeder for taping to glassfibre fishing poles and I'm prepared to accept the slightly worse losses for that convenience.

KO7I:
Hi Jenny & Vic,
I've tried a 20M double zepp, center fed with ladder line for a winter DX season once before.  It worked very well.  By shortening the antenna to that of a 20M dipole, the entire element is now a minimum of 35 ft high.  This has helped my situation out a lot.  I think this antenna, with the tuner located remotely is going to be winner. 
Now I am working on procuring a military surplus ammo can, for water proof storage of the auto tuner.  Looks like the local Cabela's store has them in stock.
I am an professional EMC engineer and I can not bring myself to operate with ladder line in my ham shack. I perform Hi Intensity RF fields compliance testing on a daily basis. There are times I run QRO power and I need to be careful of cumulative RF exposure.
I do everything I can to keep RF out of my shack.
For the average ham running 5W there is nothing to worry about.
73, Don KO7i

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